(19)
(11) EP 1 261 157 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
16.02.2005 Bulletin 2005/07

(43) Date of publication A2:
27.11.2002 Bulletin 2002/48

(21) Application number: 02077001.2

(22) Date of filing: 22.05.2002
(51) International Patent Classification (IPC)7: H04J 3/14, H04J 3/06
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 22.05.2001 US 862864

(71) Applicant: Nortel Networks Limited
St. Laurent, Quebec H4S 2A9 (CA)

(72) Inventors:
  • Courtney, John
    Belfast, Co. Antrim BT38 8XH (GB)
  • Goodman, David
    St. Albans, Herfordshire AL4 9XA (GB)
  • Carson, Mark
    Belfast, Co. Antrim BT15 5FE (GB)

(74) Representative: Anderson, Angela et al
Nortel Networks Limited IP Law Group London Road
Harlow, Essex CM17 9NA
Harlow, Essex CM17 9NA (GB)

   


(54) Hitless protection switching


(57) The invention provides a method and apparatus for providing hitless protection switching in a transmission systems which support a standardised implementation of virtual concatenation. A switching apparatus is arranged to receive data signals on at least two transmission paths and to output data from a selected one of said transmission paths. The apparatus is arranged to align the respective received data signals so that a selector mechanism can select between corresponding elements of the received data signals. This arrangement allows hitless switching to be performed since there is no loss or repetition of signal elements when switching occurs. In a preferred embodiment, data in respect of each frame of each data signal is stored and the selector mechanism selects between paths on a frame-by-frame basis by comparing quality information carried by the data signals. This arrangement offers a very low end to end Bit Error Rate (BER) performance. The invention is suitable for both synchronous and non-synchronous networks (for example, OTN)which implement standardised virtual concatenation.






Search report